The good/bad news workout revival
Does exercise increase pain for you, or is the primary incapacitating symptom the malaise / sickness feeling? I tend to have the ability to do light exercise but as I try to progress, in a very measured way, to more advanced exercises (still extremely NOT advanced), I always end-up with an 'injury' that takes me out. It's not an injury though, of course, there's no evidence of injury, but I'll have a low back that won't let me do anything (including sit) for several weeks. Which kills any progress. Or my ribs or wrist now hurt, meaning I can't do yoga, or whatever else I'm trying to work on. I do feel general malaise, though not likely to the level you're describing, but it's the pain that stops me. I honestly don't know if I should be pushing through that pain or resting it... it sounds like you pushing through didn't get you to the fabled 'other side' of it...?
Everything you describe is identical to the symptoms of autonomic dysfunction. The umbrella term is dysautonomia. There are numerous subtypes that are identified by their specific collection and intensity of certain symptoms,but there is a lot of overlap.
Dysautonomia can be caused by a viral infection of any kind, and it can take sometimes years to develop. It can also develop idiosyncratically - no identifiable reason.
The definitive criterion for diagnosis is a tilt table test done by a knowledgeable cardiologist, neurologist arrhythmia specialist.
There are specific protocols that help make it more manageable. I heartily recommend subscribing to Dr Andrew Huberman's podcast - Stanford neuroscientist. He breaks down brain and nervous system function beautifully for the lay person and always offers concrete, actionable protocols for protecting and optimizing brain and nervous system function. I have benefited from his generous outpouring of knowledge in managing and improving my autonomic function, specifically brain health . I also tell everyone I know to listen to Dr Satchin Panda, also a neuroscientist doing groundbreaking research in circadian rhythm. Always providing actionable, practical strategies for preserving and increasing our immune function, synching up the organ systems for maximum overall function. This is all hard core, concrete science, no woo woo.
With dysautonomia one's body a
has real limitations and while there are ways to maintain much functionality, there is no point whatsoever in pushing beyond the limits except to inflict misery on oneself or actual damage.
Gentle, steady conditioning is prescribed. Yes, you are discovering that you need more water -- a LOT more water. This is a classic dysautonomia symptom - dysregulation of electrolyte balance. When increasing hydration so much, most dysautonomics need extra sodium.
If you ever want to discuss any of this I'd be happy to. I hope it might help you avoid a lot of wasted time going down rabbit holes that lead to dead ends and frustration and possibly increased, unnecessary decline.